This qualitative study explores infant-family mental health experts' perspectives and experiences regarding the inclusion of infants in the family therapy setting. Infant socioemotional development is relational in nature and evolves in the context of both dyadic attachment relationships and broader multi-person co-parenting systems. Given this, we sought to understand why family therapy interventions involving families with infants rarely include the infant in a triangular or family systemic approach. Interviews were completed by clinical and/or research experts whose work integrates tenets of both infant mental health (IMH) and family theory and therapy. All interviewees brought at least 5 years of expertise and were actively engaged in the field. Interviewees expressed consistent beliefs that infants have a rightful and helpful place in family therapy approaches. They maintained that infants' innate social drive and communicative capacities position them to make meaningful and clinically significant contributions within family and systemic psychotherapy contexts. Noting that infants have remained on the periphery of these practices, experts advocated expansion and greater integration between IMH and family therapy, while preserving each field's distinctive identity. Experts reported that the interplay between IMH and family therapy fields has been uni-directional as family systems concepts are embedded within IMH approaches, but few IMH premises are incorporated in mainstream family therapy practices. The disconnect was attributed to multiple factors, including graduate and professional training and theoretical, clinical, research, and sociocultural barriers, which were mutually reinforcing. Experts also identified clinical gains for both infants and family members when infants were meaningfully included in family interventions. Common ground was identified between the disciplines, with a belief that relationally distressed young children and parents are best served by clinical engagement with their network of relationships. Results call for greater collaboration between disciplines to challenge existing traditions and to more fully include infants in mainstream family therapy. Recommendations for integration of family therapy and IMH in clinical, theoretical, research, training, and sociocultural domains are offered.